Abstract: The method consists in that a preground stock is fed in a counter-current flow relatively to the flow of electrons in a beam and is mixed directly in said beam. A mineral binder can be produced in a special apparatus wherein the stock is fed into an irradiation zone by a conveyor at the end whereof is provided a bell placed into an air-tight reaction chamber so that a source of accelerated electrons is coaxial with said bell, said source being arranged at the outlet from the bell, and disposed in the bell with provision for rotation is at least one mixing contrivance which assures uniform distribution of the stock processed at the outlet from the bell in the zone of irradiation.